docs: def output_results(results, split_id='results', output_stream=None):
      '''
      Log `results` readably to `output_stream`, with a header
      containing `split_id`.
  
      :param results: a dictionary of summary statistics from an evaluation
      :type results: dict(str -> object)
  
      :param str split_id: an identifier for the source of `results` (e.g. 'dev')
  
      :param file output_stream: the file-like object to which to log the results
          (default: stdout)
      :type split_id: str
      '''
      if output_stream is None:
          output_stream = sys.stdout
  
      output_stream.write('----- %s -----\n' % split_id)
      for name in sorted(results.keys()):
          output_stream.write('%s: %s\n' % (name, repr(results[name])))
  
      output_stream.flush()